Copper foil inspection device copper foil inspection method defect inspection device and defeat inspection method

ABSTRACT

A surface of copper foil wound onto a guide roller  26  is irradiated with light. Specular light from the copper foil surface is received by CCD cameras  14   a,  and scattered light from the copper foil surface is received by CCD cameras  14   b.  When, in a region in which the amount of specular light received by the CCD cameras  14   a  is equal to or larger than a first threshold, a portion having a luminance equal to or larger than a second threshold is present, and when the amount of scattered light received by the CCD cameras  14   b  is smaller than a luminance average, that region is determined to be a defective copper portion.

TECHNICAL FIELD

The present invention relates to a copper foil inspection apparatus anda copper foil inspection process, in which a surface of copper foil usedas a printed board for an electronic circuit is irradiated with light inorder to optically detect a defective copper portion which is likely toremain after etching of the printed board, and to a defect inspectionapparatus and a defect inspection process for specifying a defectiveportion of a sheet-like object to be inspected.

BACKGROUND ART

A variety of surface flaw inspection techniques, in which a flaw in asurface of an object to be inspected, such as a surface of a thin steelsheet, is optically detected by irradiating the surface with light andanalyzing light reflected from the surface, have been proposed.

For example, Japanese Patent Application Laid-Open (JP-A) No. 58-204353proposes a process for detecting a flaw in a surface of a metal body,wherein a surface of an object to be inspected is irradiated with light,and specular light and diffused light reflected from the surface aredetected by cameras. In this surface flaw detection process, light ismade incident on the surface of the object to be inspected at an angleof 35° to 75°, and light reflected from the surface is received by twocameras, which are disposed in a direction in which specular lightadvances and a direction which is within 20° from the direction in whichthe incident light or the specular light advances. Subsequently, signalsgenerated by the two cameras at the time of receiving light are comparedwith each other by, for example, obtaining a logical sum thereof. Onlywhen the cameras detect an abnormal value at the same time, a portionhaving the abnormal value is regarded as a flaw. In this way, thesurface flaw detection process which is not affected by noise isrealized.

Further, JP-A No. 60-228943 proposes a process for inspecting a flaw ina surface of an object to be inspected by receiving backscattering lightfrom the test substance. In this flaw inspection process, a flaw in asurface of a stainless steel sheet is detected by making light incidentonto the stainless steel sheet at a large incidence angle and detectinglight reflecting back, namely, backscattering light.

Moreover, JP-A No. 8-178867 proposes an apparatus for detecting a flawin hot-rolled flat steel by detecting a plurality of reflectedbackscattering light beams. This hot-rolled flat steel flaw detectionapparatus detects a scratch on the hot-rolled flat steel. In this flawdetection apparatus, the angle of a slope of a scratch is 10 to 40°, andplural cameras are disposed in directions in which reflectedbackscattering light beams advance, so as to receive all the specularlight reflected from the slope of the scratch having an angle within theabove range.

However, the purpose of the measuring techniques proposed above is todetect a remarkably irregular flaw. It has been difficult to reliablydetect a flaw which is formed by adhesion on copper foil and notremarkably irregular.

For example, as for the flaw detection process disclosed in JP-A No.58-204353, the two cameras for receiving specular light and scatteredlight are provided so that the influence of noise is removed byobtaining a logical sum of the detection signals generated by thecameras. Thus, the process can be used to detect remarkably irregularflaws, namely, flaws in the surface which are cracked, dug up or turnedup because signals of these flaws can be picked up by both the cameras.However, it is impossible to reliably detect flaws which are not soremarkably irregular that only one of the cameras can pick up signalsthereof.

Further, the surface condition inspection process disclosed in JP-A No.60-228943 is intended to detect raised flaws, which are conspicuous onthe stainless steel sheet having small surface roughness. Thus, thisprocess cannot be used for defects which do not have conspicuouslyraised portions.

Furthermore, the apparatus for detecting a flaw in hot-rolled flat steeldisclosed in JP-A No. 8-178867 is intended to detect scratches, and thedetection is based on the capture of specular light reflected from theslope of a scratch. Thus, reflected backscattering light of some of thedefects which are not remarkably irregular may not be captured by theapparatus.

In view of the above drawbacks, an object of the present invention is toprovide a defect inspection apparatus and a defect inspection processfor detecting with high accuracy a defect of an object to be inspected.Particularly, an object of the present invention is to provide a copperfoil inspection apparatus and a copper foil inspection process fordetecting with high accuracy a defective copper portion of a surface ofcopper foil, which portion is likely to remain after etching.

DISCLOSURE OF THE INVENTION

In order to achieve the above objects, a first aspect of the presentinvention is a copper foil inspection apparatus comprising: a lightsource for irradiating a surface of copper foil with light; firstlight-receiving means for receiving specular light from the copper foilsurface; second light-receiving means for receiving scattered light fromthe copper foil surface; and a determining portion which, when an amountof light received from a predetermined region of the copper foil surfaceby the first light-receiving means is no less than a first threshold andan amount of light received from the predetermined region by the secondlight-receiving means is no more than a second threshold which issmaller than the first threshold, determines that the predeterminedregion is a defective copper portion.

Further, a second aspect of the present invention is a copper foilinspection process comprising: irradiating a surface of a copper foilwith light; receiving specular light from the copper foil surface byfirst light-receiving means; receiving scattered light from the copperfoil surface by second light-receiving means; and determining, when anamount of light received from a predetermined region of the copper foilsurface by the first light-receiving means is no less than a firstthreshold and an amount of light received from the predetermined regionby the second light-receiving means is no more than a second thresholdwhich is smaller than the first threshold, that the predetermined regionis a defective copper portion.

Copper foil is generally manufactured by an electrolyzing step forprecipitating copper foil and a roughening step for further adheringcopper powder on a surface of the precipitated copper foil. Research bythe present inventors has revealed that the following portions of thecopper foil precipitated in the electrolyzing step are likely to remainon the printed board after etching: a portion which conspicuouslyprotrudes from the copper foil surface as compared with other portionsof the surface, or has a large protruding area (hereinafter collectivelyreferred to as the “irregularly precipitated portions”); and a portionformed such that a relatively large piece of copper is deposited in theroughening step on a portion of the copper foil surface which has beenprecipitated very finely in the electrolyzing step (hereinaftercollectively referred to as the “copper powder portions”). Thus, in thepresent invention, the irregularly precipitated portions and the copperpowder portions which are likely to remain after etching (hereinafterreferred to as the “defective copper portions”) are detected asdefective portions.

According to the first and second aspects of the present invention, thecopper foil surface is irradiated with light, specular light from thepredetermined region of the copper foil surface is received by the firstlight-receiving means, and scattered light from the predetermined regionis received by the second light-receiving means. It has become clear byexperiment that the amount of specular light from a defective copperportion of the copper foil surface is larger than the amount of specularlight from a non-defective copper portion, and that the amount ofscattered light from a defective copper portion of the surface of anobject to be inspected is smaller than the amount of scattered lightfrom a non-defective copper portion. However, since a direction in whichreflected light advances may be changed by a flaw or the like on thecopper foil surface, it is difficult to accurately determine thepresence of a defective copper portion when the determination is madebased on either the amount of reflected light or the amount of scatteredlight. Therefore, a threshold is set for the determining portion inorder to determine the presence of a defective copper portion. When thepredetermined region exists in which the amount of light received by thefirst light-receiving means is no less than the first threshold and theamount of light received by the second light-receiving means is no morethan the second threshold, the determining portion determines that thepredetermined region is a defective copper portion.

As described above, the threshold is set based on the reflectionproperty of light reflected from a defective copper portion adhering tothe copper foil surface, and the presence or absence of a defectivecopper portion is determined based on comparison of the results of thetwo types of light received, i.e., specular light and scattered light,with the respective thresholds. Thus, as compared with a case in whichthe determination is made based on either reflected light or scatteredlight, a defect caused by adhesion of the defective copper portion canbe extracted more accurately.

In the first and second aspects of the present invention, thepredetermined region can also be determined to be a defective copperportion when the predetermined region includes an area, from which anamount of light received by the first light-receiving means is no lessthan a third threshold which is larger than the first threshold.

As described above, the two thresholds are set for the specular lightreceived, and the presence of the area, from which the amount of lightreceived is no less than the third threshold, in the predeterminedregion, from which the amount of light received is no less than thefirst threshold, is added as a condition for the determination of adefective copper portion. In this way, the defective copper portion canbe detected more accurately.

Moreover, in the first and second aspects of the present invention, thepredetermined region can also be determined to be a defective copperportion when the size of the predetermined region is no less than apredetermined size.

When the defective copper portion is smaller than the predeterminedsize, the defective copper portion is often not affected by etching.Further, a portion having an abnormal value caused by noise also needsto be removed. When a region of size equal to or larger than thepredetermined size is formed by the predetermined regions eachsatisfying the condition that the amount of light received therefrom isno less than the first threshold, that region is determined to be adefective copper portion. As a result, a portion which is not affectedby etching and a portion having an abnormal value caused by noise can beremoved. Thus, the defective copper portion can be extracted moreaccurately.

The second light-receiving means according to the first and secondaspects can receive appropriate scattered light by receiving scatteredlight from the front of the surface of the object to be inspected.

In the first and second aspects of the present invention, a defectivecopper portion can be determined with higher accuracy as follows. Lightreflected from the predetermined region which has been determined to bea defective copper portion is received by third light-receiving means ofresolution higher than that of the first and second light-receivingmeans. The determining portion further distinguishes the presence orabsence of the defective copper portion based on the amount of lightreceived by the third light-receiving means, and determines that thepredetermined region is the defective copper portion when thedetermining portion distinguishes the presence of the defective copperportion. As a result, the defective copper portion can be determinedwith higher accuracy.

A third aspect of the present invention is a defect inspection apparatuscomprising: first image pickup means for picking up an image of asurface of a moving, sheet-like object to be inspected, at an upstreamside in a direction in which the object to be inspected is moved;detecting means for detecting a defective portion of the surface of theobject to be inspected based on the image which has been picked up;second image pickup means for picking up an image of the defectiveportion at a downstream side in the direction in which the object to beinspected is moved, the second image pickup means having a resolutionhigher than that of the first image pickup means; and defect determiningmeans for determining, when a defect is verified in the defectiveportion based on the image picked up by the second image pickup means,that the defect is present in the defective portion.

Further, a fourth aspect of the present invention is a defect inspectionprocess comprising: picking up, by first image pickup means, an image ofa surface of a moving, sheet-like object to be inspected, at an upstreamside in a direction in which the object to be inspected is moved;detecting a defective portion of the surface of the object to beinspected based on the image which has been picked up; picking up, bysecond image pickup means, an image of the defective portion at adownstream side in the direction in which the object to be inspected ismoved, the second image pickup means having a resolution higher thanthat of the first image pickup means; and determining, when a defect isverified in the defective portion based on the image picked up by thesecond image pickup means, that the defect is present in the defectiveportion.

According to the third and fourth aspects of the present invention, adefective portion is detected by the first image pickup means of lowresolution which picks up an image of the surface of the sheet-likeobject to be inspected. Another image of the detected defective portionis picked up by the second image pickup means having a resolution higherthan that of the first image pickup means. When a defect is verifiedbased on the image picked up by the second image pickup means, it isdetermined that a defect is present in the defective portion. Therefore,defects can be detected with higher accuracy.

Further, only the image of a portion which is determined to be defectivebased on the image picked up by the first image pickup means is pickedup by the expensive, high-resolution image pickup means. Thus, an imagepickup range can be limited, and a defect of the object to be inspectedcan be effectively detected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram of a part of a copper foilinspection apparatus according to an embodiment of the presentinvention.

FIG. 2 is a schematic block diagram of a signal processing sectionaccording to a first embodiment.

FIGS. 3A through 3C show examples of an image read by CCD sensors.

FIG. 4 is a flowchart of a process for reflected light.

FIG. 5 is a flowchart of a process for scattered light.

FIG. 6 is a flowchart of a determination process.

FIG. 7 is a view showing the positions of a high-resolution CCD cameraand copper foil.

FIG. 8 is a schematic block diagram of a signal processing sectionaccording to a second embodiment.

FIG. 9 is a flowchart of a verification process.

BEST MODE FOR CARRYING OUT THE INVENTION

A copper foil inspection apparatus of the present invention will bedescribed in detail below with reference to the drawings.

FIRST EMBODIMENT

A copper foil inspection apparatus 10 according to the presentembodiment includes, as shown in FIG. 1, light sources 12 a, 12 b and 12c, CCD sensors 14 a and 14 b, a guide roller 20, and a signal processingsection 28 (not shown in FIG. 1).

Copper foil 26 as an object to be inspected is taken out from anunillustrated copper foil manufacturing apparatus and guided via aplurality of rollers to the copper foil inspection apparatus 10. Copperfoil having, for example, a width of 1300 mm or 1350 mm and a thicknessof 12 μm, 18 μm, 35 μm or 70 μm is used as the copper foil 26. The guideroller 20 is rotated in a direction of arrow X to convey the copper foil26 as the object to be inspected. The copper foil 26 is wound along thecircumference of a lower portion of the guide roller 20 with the surfacethereof on the outer side.

The light source 12 a is disposed so as to irradiate a reading portion Pof the copper foil 26 with light (at an incidence angle of, for example,30°). The reading portion P is located at a position lower than acentral portion of the guide roller 20 in a horizontal directionthereof. The multiple (for example, six) CCD sensors 14 a are disposedalong an axial direction of the guide roller 20 and on an optical axisof specular light reflected from the reading portion P which isirradiated with the light source 12 a. The CCD sensors 14 a receive thelight reflected from the reading portion P.

An unillustrated rotary encoder 16 for outputting a pulse signal inaccordance with the rotation of the guide roller 20 is connected to arotary shaft of the guide roller 20.

The light source 12 b is disposed so as to irradiate a reading portion Qof the copper foil 26 with light (at an incidence angle of, for example,45°) The reading portion Q is located at a position lower than thecentral portion of the guide roller 20 in the horizontal directionthereof. Further, the light source 12 c is disposed at a positionopposite the position of the light 12 b with respect to a normal line ofthe reading portion Q, and irradiates the reading portion Q with light.The multiple (e.g., six) CCD sensors 14 b are disposed along the axialdirection of the guide roller 20 and in the direction of the normal lineof the reading portion Q, and receive scattered light from the readingportion Q.

As shown in FIG. 2, the signal processing section 28 includes adetermining portion 18, a reflected light processing portion 22, and ascattered light processing portion 24. The reflected light processingportion 22 is connected to the CCD sensors 14 a and the determiningportion 18, while the scattered light processing portion 24 is connectedto the CCD sensors 14 b and the determining portion 18. The rotaryencoder 16 is connected to the guide roller 20 and the determiningportion 18. Each of the reflected light processing portion 22, thescattered light processing portion 24, and the determining portion 18can be formed by a microcomputer including a CPU, a ROM and a RAM.

Operation of the present embodiment will be described next.

When an instruction to start up the copper foil inspection apparatus 10is given to an unillustrated driving portion, the guide roller 20 isrotated in the direction of X, thereby starting conveyance of the copperfoil 26. At the same time, the light source 12 a irradiates the readingportion P of the copper foil 26 with light at an incidence angle of, forexample, 30°, and the CCD sensors 14 a receive light reflected from thereading portion P of the copper foil 26 and advancing diagonally fromthe reading portion P, namely, specular light, at a light-receivingangle of 30°. The light sources 12 b and 12 c irradiate the readingportion Q of the copper foil 26 with light at an incidence angle of, forexample, 45°, and the CCD sensors 14 b receive scattered light from thereading portion Q at the front thereof, namely, at a light-receivingangle of 0°. As shown in FIG. 3A, light is received in predeterminedunits of the width W and the length H of the copper foil 26. The CCDsensors 14 a and 14 b transmit to the reflected light processing portion22 and the scattered light processing portion 24 image data obtained byconverting each pixel into an 8-bit luminance signal in accordance withthe intensity of the light received.

Upon receiving the image data from the CCD sensor 14 a, the reflectedlight processing portion 22 executes a process for reflected light shownin FIG. 4.

Image data is received in step 80, and an average of the luminance ofthe image data received is calculated in step 82. In step 84, theluminance average calculated is multiplied by, for example, 1.3. In thisway, a first value which is obtained by multiplying the luminanceaverage by a predetermined value is used as a first threshold.

It has become clear by experiments that a defective copper portion ofthe copper foil 26 has a larger amount of reflected light than anon-defective portion of the copper foil surface. Namely, a defectivecopper portion has a luminance higher than that of a non-defectivecopper portion, and looks whitish to the human eye. Thus, in the imagedata received, a portion having high luminance is likely to be adefective copper portion.

For this reason, in step 86, a white label processing is carried out foreach region formed by pixels of luminance larger than the value obtainedby multiplying the luminance average by 1.3, when the first thresholdis, for example, 1.3 times the calculated luminance average. Thewhite-labeled region indicates a region of high luminance. In step 88, asomewhat large white-labeled region, namely, a somewhat large regionformed by white-labeled pixels, is extracted. Since some noise isgenerated in the image data converted by the CCD sensors 14 a, a pixelof high luminance may be formed by the noise and erroneously labeledwhite even when this pixel does not form a defective copper portion.Further, the irregularly precipitated portions or copper powder portionswhich are small and not affected by etching may be formed on the copperfoil. Thus, this processing is intended to remove noise and these smallportions. Specifically, filtering for extracting only white-labeledregions of the predetermined size or larger is performed, such thatwhite-labeled regions smaller than the predetermined size are removed.The predetermined size is set in view of the accuracy of the CCD sensors14 a, and the size of the irregularly precipitated portions or copperpowder portions, which should be removed as defects.

In the image picked up by the CCD sensors 14 a, when a pixel having aluminance of a predetermined value or more is present among the pixelsforming the white-labeled region of the predetermined size or larger,namely, when, in a region of somewhat high luminance, there is a portionof higher luminance, there is a high possibility that etching residuewill be formed. Thus, in step 90, a luminance which is, for example, 1.7times the luminance average is determined. The luminance which is 1.7times the luminance average, namely, a second value which is obtained bymultiplying the luminance average by a predetermined value and is largerthan the first value obtained by multiplying the luminance average by apredetermined value is used as a second threshold. In step 92, only awhite-labeled region, in which a pixel of luminance larger than thesecond threshold is present among the white-labeled pixels forming thelabeled region of the predetermined size or larger, is extracted, and awhite-labeled region having no pixel of luminance larger than the secondthreshold is excluded. Labeling and filtering may also be carried outfor pixels of luminance larger than the second threshold in the same wayas described above, and only a region of predetermined size or largermay be used as an object of determination. Subsequently, in step 94, theimage subjected to the white label processing is outputted to thedetermining portion 18, and this process ends.

An example of the image picked up by the CCD sensors 14 a, an example ofthe image obtained after step 88 in the process for reflected light, andan example of the image obtained after the process for reflected lightare illustrated in (1), (2) and (3) in FIG. 3A, respectively. In theimage data picked up by the CCD sensors 14 a, 1, m, s and o arerecognized as portions having a luminance larger than the value obtainedby multiplying the average by 1.3 ((1)). However, after step 88, theportion o which is smaller than the predetermined size is removed, andthe portions l, s and m remain ((2)). After the process ends, theportion m having no pixels of luminance larger than the value obtainedby multiplying the average by 1.7 is removed, and the portions l and mare extracted ((3)). These portions are estimated to be defectiveportions.

According to the process for reflected light, a region, in which aportion having a luminance equal to or larger than the second valueobtained by multiplying the luminance average by a predetermined valueis present among the portions which are equal to or larger than thefirst value obtained by multiplying the luminance average by apredetermined value and are equal to or larger than the predeterminedsize, is extracted.

The scattered light processing portion 24 executes a process forscattered light shown in FIG. 5 upon receiving the image data from theCCD sensors 14 b.

The image data is received in step 60, and an average of the luminanceof the image data received is calculated in step 62. The luminanceaverage of the image data can be calculated by dividing by the number ofpixels the total of the luminance of all pixels within an area definedby the width W and the length H of the copper foil 26.

It has become clear by experiments that a defective portion of thecopper foil 26 has a smaller amount of scattered light than anon-defective portion of the copper foil surface. Namely, a defectivecopper portion has a luminance lower than that of a non-defective copperportion, and looks dark to the human eye. Thus, in the image datareceived, a portion having low luminance is likely to be a defectivecopper portion. For this reason, in step 64, a black label processing iscarried out for each region formed by pixels of luminance smaller thanthe calculated luminance average, which is used as a threshold. In step66, a black-labeled region of predetermined size or larger, namely, asomewhat large region formed by black-labeled pixels, is extracted.Since some noise is generated in the image data converted by the CCDsensors 14 b, a pixel of low luminance may be formed by the noise anderroneously labeled black even when this pixel does not form a defectivecopper portion. Further, the irregularly precipitated portions or copperpowder portions which are small and not affected by etching may beformed on the copper foil. Thus, this processing is intended to removenoise and these small portions. Specifically, filtering for extractingonly black-labeled regions of the predetermined size or larger isperformed, such that black-labeled regions smaller than thepredetermined size are removed. In step 68, the image subjected to theblack label processing is outputted to the determining portion 18, andthis process ends.

While the luminance average of each image received is used as thethreshold in the above description, other thresholds may be set and usedto detect a defective copper portion. Further, the above-describedpredetermined size is set in view of the accuracy of the CCD sensors 14b, and the size of defective copper portions, which should be removed asdefects.

An example of the image picked up by the CCD sensors 14 b, and anexample of the image obtained after the process for scattered light areillustrated in (1) and (2) in FIG. 3B, respectively. In the image datapicked up by the CCD sensors 14 b, L, M, S and O are recognized asportions having a luminance smaller than the average. The portion Swhich is smaller than the predetermined size is removed by this process,and the portions L, M and O are estimated to be defective portions.

According to the process for scattered light, a portion which has a lowluminance and is equal to or larger than the predetermined size can beextracted.

The determining portion 18 receives image data A and image data B fromthe reflected light processing portion 22 and the scattered lightprocessing portion 24, respectively, and executes a process forextracting a defective portion of the copper foil 26.

The copper foil 26 is conveyed by the guide roller 20 and read at thereading positions P and Q by the CCD sensors 14 a and 14 b,respectively. Thus, a difference exists in the time at which anidentical portion of the copper foil 26 is read by the CCD sensors 14 aand 14 b. Therefore, in step 100, the time interval is measured bycounting pulse signals which are obtained by the rotary encoder 16 andcorrespond to the rotational speed of the guide roller 20, the imagedata B which is received after the image data A at this predeterminedtime interval is determined as the image data for the identical portionof the copper foil 26, and then pairing of the image data A and theimage data B for the identical portion of the copper foil 26 is carriedout. In step 102, the paired image data A and image data B are comparedwith each other, and a region which has been labeled black in the imagedata A and labeled white in the image data B is extracted as a defectivecopper portion. In step 104, the extracted portion is outputted, and theprocess ends.

FIG. 3C shows an example of an image obtained after the extractionprocess. Among the portions L, M and O extracted in the process forscattered light, and the portions l and s extracted in the process forreflected light, the portion O which has been extracted only in theprocess for scattered light and not in the process for reflected lightis removed, and the portions L-l and M-s commonly extracted in both theprocesses are extracted.

According to the present embodiment, a first estimation and a secondestimation are carried out. In the first estimation, a defective copperportion is estimated based on the image data obtained by reading, at theposition located in the oblique direction of the copper foil 26, lightreflected from the copper foil 26. In the second estimation, a defectivecopper portion is estimated based on the image data obtained by reading,at the position located at the front of the copper foil 26, scatteredlight from the copper foil 26. Subsequently, a portion estimated to be adefective copper portion by both the first and second estimations isdetermined as the defective copper portion. Thus, a defective copperportion on the surface of the copper foil 26 can be reliably extractedwith higher accuracy.

SECOND EMBODIMENT

A second embodiment will be described next. Components of the presentsecond embodiment which are similar to those of the first embodiment aredesignated by the same reference numerals, and detailed descriptionthereof will be omitted.

A copper foil inspection apparatus 11 according to the presentembodiment includes all the components of the copper foil inspectionapparatus 10 according to the first embodiment shown in FIG. 1. Further,as shown in FIG. 7, a CCD camera 15 having resolution higher than thatof the CCD sensors used in the first embodiment, and a light source 13are disposed downstream from the copper foil surface inspectionpositions of the first embodiment in the direction in which the copperfoil 26 is moved. Furthermore, as shown in FIG. 8, the determiningportion 18 is connected to a verification processing portion 25, whichin turn is connected to the CCD camera 15. The CCD camera 15 is disposedso as to be movable in the width W direction of the copper foil 26 andpick up an image of the surface of the copper foil 26 in an orientationperpendicular thereto. The light source 13 which is ring-shaped andirradiates the copper foil 26 with light is disposed at the periphery ofthe CCD camera 15. Further, the CCD camera 15 is also connected to thedetermining portion 18.

After a defective copper portion is extracted in the same way as in thefirst embodiment, the determining portion 18 transmits information onthe position of the extracted defective portion (hereinafter referred toas the “assumed defective portion”) to an unillustrated driving portionof the CCD camera 15, such that the CCD camera 15 is moved to a positionat which the CCD camera 15 can pick up an image of the assumed defectiveportion. The light source 13 emits light when the assumed defectiveportion is moved and disposed under the light source 13, and the CCDcamera 15 picks up an image of the surface of the assumed defectiveportion. The image thus picked up is transmitted to the verificationprocessing portion 25, where a verification process is performed inaccordance with a flowchart shown in FIG. 9.

The image is received in step 110, and a luminance average of thereceived image is calculated in step 112. The image which has beenpicked up is characterized in that, for example, the defective copperportion has a black central portion and a white portion surrounding theblack central portion. Thus, in step 114, a luminance threshold for aportion surrounding a portion to be extracted as a defective portion iscalculated by multiplying the luminance average by 1.3, and, in step116, a luminance threshold for the central portion of the portion to beextracted as a defective portion is calculated by multiplying theluminance average by 0.2. In step 118, the white label processing iscarried out for each region formed by pixels of luminance larger thanthe value obtained by multiplying the luminance average by 1.3. In step120, only a white-labeled region having a pixel of luminance smallerthan the value obtained by multiplying the luminance average by 0.2 isextracted from among white-labeled regions, and other white-labeledregions are removed. Subsequently, the image which has been subjected tothe white label processing is outputted in step 122, and the processends. A white-labeled region of the output image can be determined as adefective copper portion.

According to the present embodiment, since the defective copper portionwhich is previously extracted is further verified by the CCD camera ofhigher resolution, defective copper portions can be extracted withhigher accuracy. Moreover, the expensive, high-resolution CCD camerapicks up an image of only a portion which is previously determined as adefective portion based on the image picked up. Thus, an image pickuprange can be limited, and a defect of the copper foil can be effectivelydetected.

While a defective copper portion of the surface of a copper foil isextracted in the present embodiment, the present invention is notlimited thereto. An image of the surface of a moving, sheet-like objectto be inspected is picked up at an upstream side by a low-resolution CCDcamera, and an assumed defective portion is detected based on the pickupimage. Thereafter, an image of the assumed defective portion detected isfurther picked up at a downstream side by a high-resolution CCD camera.When it is determined that a defect exists based on the pickup image,the determination can be made that a defect is present in the detectedportion. In addition to the copper foil, examples of the sheet-likeobject to be inspected include paper and CSP, and the present inventioncan be applied to these objects.

1. A copper foil inspection apparatus comprising: a light source for irradiating a surface of copper foil with light; first light-receiving means for receiving specular light from the copper foil surface; second light-receiving means for receiving scattered light from the copper foil surface; and a determining portion which, when an amount of light received from a predetermined region of the copper foil surface by the first light-receiving means is no less than a first threshold and an amount of light received from the predetermined region by the second light-receiving means is no more than a second threshold which is smaller than the first threshold, determines that the predetermined region is a defective copper portion.
 2. The copper foil inspection apparatus of claim 1, wherein the determining portion determines that the predetermined region is a defective copper portion when the predetermined region includes an area, from which an amount of light received by the first light-receiving means is no less than a third threshold which is larger than the first threshold.
 3. The copper foil inspection apparatus of claim 1, wherein the determining portion determines that the predetermined region is a defective copper portion when the size of the predetermined region is no less than a predetermined size.
 4. The copper foil inspection apparatus of claim 1, wherein the second light-receiving means receives scattered light from the front of a surface to be inspected.
 5. The copper foil inspection apparatus of claim 1, further comprising third light-receiving means for receiving light reflected from the predetermined region which has been determined to be a defective copper portion, the third light-receiving means having a resolution higher than that of the first and second light-receiving means, wherein the determining portion further distinguishes the presence or absence of the defective copper portion based on the amount of light received by the third light-receiving means, and determines that the predetermined region is the defective copper portion when the determining portion distinguishes the presence of the defective copper portion.
 6. A copper foil inspection process comprising: irradiating a surface of a copper foil with light; receiving specular light from the copper foil surface by first light-receiving means; receiving scattered light from the copper foil surface by second light-receiving means; determining, when an amount of light received from a predetermined region of the copper foil surface by the first light-receiving means is no less than a first threshold and an amount of light received from the predetermined region by the second light-receiving means is no more than a second threshold which is smaller than the first threshold, that the predetermined region is a defective copper portion; and outputting a signal identifying the predetermined region.
 7. The copper foil inspection process of claim 6, wherein, in the determining step, the predetermined region is determined to be a defective copper portion when the predetermined region includes an area, from which an amount of light received by the first light-receiving means is no less than a third threshold which is larger than the first threshold.
 8. The copper foil inspection process of claim 6, wherein, in the determining step, the predetermined region is determined to be a defective copper portion when the size of the predetermined region is no less than a predetermined size.
 9. The copper foil inspection process of claim 6, wherein the second light-receiving means receives scattered light from the front of a surface to be inspected.
 10. The copper foil inspection process of claim 9, further comprising receiving light reflected from the predetermined region which has been determined to be a defective copper portion, by third light-receiving means having a resolution higher than that of the first and second light-receiving means, wherein, in the determining step, the presence or absence of the defective copper portion is distinguished based on the amount of light received by the third light-receiving means, and the predetermined region is determined to be the defective copper portion when the presence of the defective copper portion is distinguished. 